fix(renderer): treat single newlines as soft breaks, not line breaks

[shmuelzon]

The renderer appended a hard newline after every source line, so a single newline inside a paragraph rendered as a visible line break. CommonMark treats it as a soft break — rendered as a space.

Add MarkdownRenderer.joinSoftBreaks, a pre-pass that joins consecutive paragraph lines into one logical line before per-line rendering:

• hard breaks still work: two+ trailing spaces, or a trailing backslash (odd runs only — an even run is escaped literal backslashes)
• a list/task item starts its own line but absorbs the plain lines that follow it (CommonMark lazy continuation), so wrapped item text stays inside the item under its hanging indent instead of dropping to the left margin as a bogus paragraph
• headers, rules, and blank lines keep their own line and never absorb or become a continuation
• a continuation line's leading/trailing whitespace is collapsed into the single joining space

Blockquote and alert bodies did the same per-line joining, so they now run their lines through the same pre-pass.

[b451c]

Merged - thank you, this is exactly the kind of fix I like to receive. The pre-pass approach keeps renderLine untouched, classify mirroring the renderer's dispatch is the right guard against gluing structural lines, and the odd/even trailing-backslash rule plus lazy continuation for list items show you went to the spec rather than the symptom. The 13 tests document the contract better than a comment ever could.

Verified locally: full suite green (108/108), Release build clean, and a running build renders one-sentence-per-line paragraphs as a single flow, two-space and backslash hard breaks still break, escaped backslashes stay literal, wrapped bullet/ordered/task items hang under their text, and blockquotes/alerts keep their paragraph structure. Search highlighting is unaffected since it works on the rendered text.

This is a visible behavior change for anyone who relied on single newlines breaking lines, so it will be called out in the changelog. Ships in the next release (1.8.0).

[b451c]

v1.8.0 with this change is now live: https://github.com/b451c/quickmd/releases/tag/v1.8.0 - thanks again!

One follow-up landed alongside it: the printable blockquote and alert views used for PDF export and printing now run the same soft-break pre-pass, so screen and PDF agree (6599cf7).

[shmuelzon]

Merged - thank you, this is exactly the kind of fix I like to receive

:)

v1.8.0 with this change is now live: https://github.com/b451c/quickmd/releases/tag/v1.8.0 - thanks again!

Nice catch, forgot about PDFs, and thanks for the quick release!